Data-Structures-And-Algorithms-Hacktoberfest18/Trees/Checking is tree BST.cpp at dd84d11d39b567f43fb1ebea5601129d3c188658 · yshshrm/Data-Structures-And-Algorithms-Hacktoberfest18 · GitHub

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#include<iostream>
#include<string>
#include<queue>
using namespace std;

struct BSTNode
{
	int data;
	BSTNode *left;
	BSTNode *right;

};

struct BSTNode *GetNewNode(int data)
{
	struct BSTNode *NewNode = new BSTNode();
	NewNode->data=data;
	NewNode->left = NULL ;
	NewNode->right = NULL;

	return NewNode;
}

struct BSTNode *Insert(BSTNode* root, int data)
{
	if(root==NULL)
		root= GetNewNode(data);

	else if(data <= root->data)
		root->left = Insert(root->left , data);

	else
		root->right = Insert(root->right , data);

	return root;
}

bool IsSubtreeLesser(BSTNode *root , int d)
{
	if(root==NULL)
		return 1;

	else if(root->data<=d && IsSubtreeLesser(root->left , d) &&IsSubtreeLesser(root->right , d))
		return 1;

	else
		return 0;

}

bool IsSubtreeGreater(BSTNode *root , int d)
{
	if(root==NULL)
		return 1;

	else if(root->data >d && IsSubtreeGreater(root->left , d) &&IsSubtreeGreater(root->right , d))
		return 1;

	else
		return 0;

}


bool IsBST(BSTNode *root)
{
	if(root==NULL)
		return 1;

	else if(IsSubtreeLesser(root->left , root->data) && IsSubtreeGreater(root->right,root->data) && IsBST(root->left) && IsBST(root->right))
	return 1;

	else
	return 0;


}


int main()
{
	struct BSTNode *rootPtr = NULL;

	rootPtr = Insert(rootPtr , 5);
	rootPtr = Insert(rootPtr , 7);
	rootPtr = Insert(rootPtr , 4);
	rootPtr = Insert(rootPtr , 15);
	rootPtr = Insert(rootPtr , 17);
	rootPtr = Insert(rootPtr , 14);
	rootPtr = Insert(rootPtr , 11);

	if(IsBST(rootPtr))
		cout<<"Tree is BST.";
	else
		cout<<"Tree is not BST.";


return 0;
}